REW is a good tool for getting in-room measurements.
It's free and fairly simple to use. And can help you spot problem areas in your room, like room modes, or more glaring issues, like a big dip in the midrange, because polarity was flipped by accident, creating a massive hole in the measured response.
But for accurate speakers measurements, you need to take the speakers outside in an open area, and get them off the ground. The higher, the more accurate the measurements will be.
Otherwise, you'll need to get your hands on a program like Clio/Clio Pocket or Klippel and take the time to learn the program and how to use gated time windows to get accurate measurements.
It also helps to have an amplifier with a Watt meter on it so you know when you're using 1 Watt.
